Fetal Electrocardiography

Abstract

This study in fetal electrocardiography was undertaken to evaluate the clinical accuracy of a simple, inexpensive preamplifier and a standard electrocardiograph. Two hundred and fifty-four patients were studied. These were divided into three groups. In group 1, consisting of 200 patients with normal pregnancy, positive fetal electrocardiograms (ECG) were recorded in 179 (89.5%), including one set of clinically unsuspected twins. In group 2, of ten patients in normal active labor, positive tracings were obtained in all ten between uterine contractions and in nine during contractions as well. Group 3 consisted of 44 diagnostic problem patients (suspected fetal death, twin pregnancy, pseudocyesis, hydatid mole, and arrhythmia) ; fetal electrocardiography established a correct diagnosis in 42 cases (95%).THE CLINICAL VALUE and research applica¬ tion of fetal electrocardiography have been re¬ cently reviewed and various recorders and tech¬ niques described.110 An inexpensive preamplifier and a standard electrocardiograph, equipment that is readily available to most hospitals, was used in this study. While this manuscript was in prepara¬ tion, a similar method was reported by Shubeck." Equipment and Technique A preamplifier capable of amplifying an input signal 50 times was modified to permit recording in the frequency range of 12 to 20 cycles per second. This modification was an outgrowth of our prelimi¬ nary studies which indicated that recording in the 12 to 20 CPS range filters out most of the baseline interference and gives clear-cut delineation of the fetal QRS complex.Additional equipment included a bipolar lead, 30-mm German silver suction cup electrodes, sev¬ eral ground wires, standard electrode paste, and a standard electrocardiograph equipped with a 50-mm/sec paper speed.Before we obtained a fetal electrocardiogram (ECG) the patient was made to feel at ease to decrease baseline interference. The procedure was briefly explained and the patient assured that no harm would come to her or the baby during the test. After voiding, the patient assumed the re¬ cumbent position and one electrode of the bipolar lead was placed in the midline of tbe abdomen at the level of the uterine fundus. The other electrode was attached just above the symphysis pubis. These positions are illustrated in Fig 1. A grounding elec¬ trode was placed in the flank. Fig 1 .-The midline (M to O) and alternate diagonal ID to 0) elec¬ trode positions used in obtaining fetal ECG.Student